Accounting for Leases as a Lessor - Allowance for Doubtful Accounts for Financing Receivables (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Apr. 30, 2020	Oct. 31, 2019
Allowance for doubtful accounts
Balance at beginning of period	$ 131	$ 120
Provision for doubtful accounts	12	33
Write-offs	(17)	(22)
Balance at end of period	$ 126	$ 131